BARCELONA – Adding the immune checkpoint inhibitor atezolizumab (Tecentriq) to standard platinum-based chemotherapy was associated with a small but statistically significant progression-free survival benefit for patients with previously untreated metastatic urothelial carcinoma, investigators in the IMvigor130 trial found.
Among 1,213 patients with newly diagnosed metastatic urothelial carcinoma assigned to receive either atezolizumab monotherapy or chemotherapy with a platinum compound and gemcitabine plus either atezolizumab or placebo, the median progression-free survival (PFS) at a median follow-up of 11.8 months was 8.2 months with atezolizumab/chemotherapy, compared with 6.3 months with chemotherapy plus placebo, reported Enrique Grande, MD, of MD Anderson Cancer Center Madrid.
“IMvigor130 is the first immune checkpoint inhibitor study to demonstrate an improvement in progression-free survival over the standard of care in first-line metastatic urothelial carcinoma. At this interim analysis, we observed a clinically meaningful improvement in the overall survival for the combination of atezolizumab plus chemotherapy that did not meet the prespecified interim boundary for significance,” he said at the European Society for Medical Oncology Congress.
Median overall survival (OS) at the interim analysis was 16.0 months in the atezolizumab arm, vs. 13.4 months in the placebo arm, translating into a hazard ratio (HR) of 0.83 trending in favor of the combination. But as noted by Dr. Grande, the P value was .027, which did not reach the interim efficacy boundary of .007.
IMvigor130 investigators enrolled patients with locally advanced metastatic urothelial carcinoma with no prior systemic therapy in the metastatic setting who had good performance status (ECOG 2 or less) and were eligible for chemotherapy with either cisplatin or carboplatin plus gemcitabine.
The patients were stratified by programmed death ligand-1 (PD-L1) status, prognostic (Bajorin) risk factor scores, and investigator choice of cisplatin or carboplatin, and then randomized to either atezolizumab plus chemotherapy, atezolizumab monotherapy, or placebo plus chemotherapy.
As noted, the co-primary endpoint of PFS in the chemotherapy arms in the intention-to-treat population was statistically significant at the preplanned interim analysis, but the other primary endpoint of OS had not reached significance.
At the time of the data cutoff in May 2019, the stratified HR for progression with atezolizumab was 0.82 (P = .007).
An analysis by subgroup showed either significant benefit or a trend favoring atezolizumab across all stratification factors, Dr. Grande said.
A hierarchical analysis of atezolizumab monotherapy vs. chemotherapy in the placebo-control arm showed a median OS of 15.7 vs. 13.1 months, respectively, with a hazard ratio of 1.02 (nonsignificant).
The benefit of atezolizumab appeared to be almost entirely among patients whose tumors had higher levels of PD-L1 expression according to immunohistochemistry (IC). The interim OS among patients with PD-L1 IC0/1 was a median of 13.5 months with atezolizumab vs. 12.9 months with chemotherapy alone, with an unstratified HR of 1.07 (nonsignificant). In contrast, among patients with PD-L1 IC2/3 status, the median OS was not reached for patients in the atezolizumab arm, vs. 17.8 months in the chemotherapy alone arm, for a stratified HR of 0.68, although this too did not reach statistical significance.
Responses were similar between the two chemotherapy arms, with an overall response rate (ORR) of 47% with atezolizumab added, vs. 44% with placebo added. The complete response (CR) rates were 13% and 7%, respectively. The ORR in the monotherapy arm was 23%, consisting of 6% complete and 17% partial responses.
Grade 3 or 4 treatment-related adverse events occurred in 81% of patients in each chemotherapy arm, compared with 15% in the atezolizumab monotherapy arm. Nine patients in the atezolizumab/chemotherapy arm died from a treatment-related cause, compared with four in the chemotherapy alone arm, and three in the atezolizumab monotherapy arm.
Adverse events leading to treatment discontinuation occurred in one-fourth of patients in each chemotherapy-containing arm, vs. less than 1% of patients in the monotherapy arm.
“The results from the IMvigor130 trial support the use of atezolizumab in combination with chemotherapy as an important new treatment option for patients with untreated metastatic urothelial carcinoma,” Dr. Grande concluded.
But invited discussant Thomas Powles, MD, of Barts Cancer Institute in London, cautioned that more data are needed to conclude that the addition of atezolizumab should become a standard of care.
“Does this change practice? Well, the for and against: significant delay in PFS, but how meaningful is that? OS trending the right way, but not significant yet. CR rates, yes with 13% CRs, but response rates weren’t very different from one another, and as response rates are similar, it’s hard to argue that the two are synergistic together, for example,” he said.
He added that the adverse event profiles “actually are very acceptable to me, and I’m really looking forward to the quality-of-life data.”
The IMvigor130 study is sponsored by F. Hoffman-La Roche. Dr. Grande disclosed honoraria and research grants from Roche and others. Dr. Powles disclosed research funding, honoraria, and travel costs from Roche and others.
SOURCE: Grande E et al. ESMO 2019. Abstract LBA14_PR.